arch/powerpc/mm/ptdump/ptdump.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2016, Rashmica Gupta, IBM Corp.
   4  *
   5  * This traverses the kernel pagetables and dumps the
   6  * information about the used sections of memory to
   7  * /sys/kernel/debug/kernel_pagetables.
   8  *
   9  * Derived from the arm64 implementation:
  10  * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
  11  * (C) Copyright 2008 Intel Corporation, Arjan van de Ven.
  12  */
  13 #include <linux/debugfs.h>
  14 #include <linux/fs.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/io.h>
  17 #include <linux/mm.h>
  18 #include <linux/highmem.h>
  19 #include <linux/sched.h>
  20 #include <linux/seq_file.h>
  21 #include <asm/fixmap.h>
  22 #include <linux/const.h>
  23 #include <asm/page.h>
  24 #include <asm/hugetlb.h>
  25
  26 #include <mm/mmu_decl.h>
  27
  28 #include "ptdump.h"
  29
  30 /*
  31  * To visualise what is happening,
  32  *
  33  *  - PTRS_PER_P** = how many entries there are in the corresponding P**
  34  *  - P**_SHIFT = how many bits of the address we use to index into the
  35  * corresponding P**
  36  *  - P**_SIZE is how much memory we can access through the table - not the
  37  * size of the table itself.
  38  * P**={PGD, PUD, PMD, PTE}
  39  *
  40  *
  41  * Each entry of the PGD points to a PUD. Each entry of a PUD points to a
  42  * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to
  43  * a page.
  44  *
  45  * In the case where there are only 3 levels, the PUD is folded into the
  46  * PGD: every PUD has only one entry which points to the PMD.
  47  *
  48  * The page dumper groups page table entries of the same type into a single
  49  * description. It uses pg_state to track the range information while
  50  * iterating over the PTE entries. When the continuity is broken it then
  51  * dumps out a description of the range - ie PTEs that are virtually contiguous
  52  * with the same PTE flags are chunked together. This is to make it clear how
  53  * different areas of the kernel virtual memory are used.
  54  *
  55  */
  56 struct pg_state {
  57         struct seq_file *seq;
  58         const struct addr_marker *marker;
  59         unsigned long start_address;
  60         unsigned long start_pa;
  61         unsigned long last_pa;
  62         unsigned long page_size;
  63         unsigned int level;
  64         u64 current_flags;
  65         bool check_wx;
  66         unsigned long wx_pages;
  67 };
  68
  69 struct addr_marker {
  70         unsigned long start_address;
  71         const char *name;
  72 };
  73
  74 static struct addr_marker address_markers[] = {
  75         { 0,    "Start of kernel VM" },
  76 #ifdef MODULES_VADDR
  77         { 0,    "modules start" },
  78         { 0,    "modules end" },
  79 #endif
  80         { 0,    "vmalloc() Area" },
  81         { 0,    "vmalloc() End" },
  82 #ifdef CONFIG_PPC64
  83         { 0,    "isa I/O start" },
  84         { 0,    "isa I/O end" },
  85         { 0,    "phb I/O start" },
  86         { 0,    "phb I/O end" },
  87         { 0,    "I/O remap start" },
  88         { 0,    "I/O remap end" },
  89         { 0,    "vmemmap start" },
  90 #else
  91         { 0,    "Early I/O remap start" },
  92         { 0,    "Early I/O remap end" },
  93 #ifdef CONFIG_HIGHMEM
  94         { 0,    "Highmem PTEs start" },
  95         { 0,    "Highmem PTEs end" },
  96 #endif
  97         { 0,    "Fixmap start" },
  98         { 0,    "Fixmap end" },
  99 #endif
 100 #ifdef CONFIG_KASAN
 101         { 0,    "kasan shadow mem start" },
 102         { 0,    "kasan shadow mem end" },
 103 #endif
 104         { -1,   NULL },
 105 };
 106
 107 #define pt_dump_seq_printf(m, fmt, args...)     \
 108 ({                                              \
 109         if (m)                                  \
 110                 seq_printf(m, fmt, ##args);     \
 111 })
 112
 113 #define pt_dump_seq_putc(m, c)          \
 114 ({                                      \
 115         if (m)                          \
 116                 seq_putc(m, c);         \
 117 })
 118
 119 void pt_dump_size(struct seq_file *m, unsigned long size)
 120 {
 121         static const char units[] = "KMGTPE";
 122         const char *unit = units;
 123
 124         /* Work out what appropriate unit to use */
 125         while (!(size & 1023) && unit[1]) {
 126                 size >>= 10;
 127                 unit++;
 128         }
 129         pt_dump_seq_printf(m, "%9lu%c ", size, *unit);
 130 }
 131
 132 static void dump_flag_info(struct pg_state *st, const struct flag_info
 133                 *flag, u64 pte, int num)
 134 {
 135         unsigned int i;
 136
 137         for (i = 0; i < num; i++, flag++) {
 138                 const char *s = NULL;
 139                 u64 val;
 140
 141                 /* flag not defined so don't check it */
 142                 if (flag->mask == 0)
 143                         continue;
 144                 /* Some 'flags' are actually values */
 145                 if (flag->is_val) {
 146                         val = pte & flag->val;
 147                         if (flag->shift)
 148                                 val = val >> flag->shift;
 149                         pt_dump_seq_printf(st->seq, "  %s:%llx", flag->set, val);
 150                 } else {
 151                         if ((pte & flag->mask) == flag->val)
 152                                 s = flag->set;
 153                         else
 154                                 s = flag->clear;
 155                         if (s)
 156                                 pt_dump_seq_printf(st->seq, "  %s", s);
 157                 }
 158                 st->current_flags &= ~flag->mask;
 159         }
 160         if (st->current_flags != 0)
 161                 pt_dump_seq_printf(st->seq, "  unknown flags:%llx", st->current_flags);
 162 }
 163
 164 static void dump_addr(struct pg_state *st, unsigned long addr)
 165 {
 166         unsigned long delta;
 167
 168 #ifdef CONFIG_PPC64
 169 #define REG             "0x%016lx"
 170 #else
 171 #define REG             "0x%08lx"
 172 #endif
 173
 174         pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
 175         if (st->start_pa == st->last_pa && st->start_address + st->page_size != addr) {
 176                 pt_dump_seq_printf(st->seq, "[" REG "]", st->start_pa);
 177                 delta = st->page_size >> 10;
 178         } else {
 179                 pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
 180                 delta = (addr - st->start_address) >> 10;
 181         }
 182         pt_dump_size(st->seq, delta);
 183 }
 184
 185 static void note_prot_wx(struct pg_state *st, unsigned long addr)
 186 {
 187         pte_t pte = __pte(st->current_flags);
 188
 189         if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx)
 190                 return;
 191
 192         if (!pte_write(pte) || !pte_exec(pte))
 193                 return;
 194
 195         WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
 196                   (void *)st->start_address, (void *)st->start_address);
 197
 198         st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
 199 }
 200
 201 static void note_page_update_state(struct pg_state *st, unsigned long addr,
 202                                    unsigned int level, u64 val, unsigned long page_size)
 203 {
 204         u64 flag = val & pg_level[level].mask;
 205         u64 pa = val & PTE_RPN_MASK;
 206
 207         st->level = level;
 208         st->current_flags = flag;
 209         st->start_address = addr;
 210         st->start_pa = pa;
 211         st->page_size = page_size;
 212
 213         while (addr >= st->marker[1].start_address) {
 214                 st->marker++;
 215                 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 216         }
 217 }
 218
 219 static void note_page(struct pg_state *st, unsigned long addr,
 220                unsigned int level, u64 val, unsigned long page_size)
 221 {
 222         u64 flag = val & pg_level[level].mask;
 223         u64 pa = val & PTE_RPN_MASK;
 224
 225         /* At first no level is set */
 226         if (!st->level) {
 227                 pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
 228                 note_page_update_state(st, addr, level, val, page_size);
 229         /*
 230          * Dump the section of virtual memory when:
 231          *   - the PTE flags from one entry to the next differs.
 232          *   - we change levels in the tree.
 233          *   - the address is in a different section of memory and is thus
 234          *   used for a different purpose, regardless of the flags.
 235          *   - the pa of this page is not adjacent to the last inspected page
 236          */
 237         } else if (flag != st->current_flags || level != st->level ||
 238                    addr >= st->marker[1].start_address ||
 239                    (pa != st->last_pa + st->page_size &&
 240                     (pa != st->start_pa || st->start_pa != st->last_pa))) {
 241
 242                 /* Check the PTE flags */
 243                 if (st->current_flags) {
 244                         note_prot_wx(st, addr);
 245                         dump_addr(st, addr);
 246
 247                         /* Dump all the flags */
 248                         if (pg_level[st->level].flag)
 249                                 dump_flag_info(st, pg_level[st->level].flag,
 250                                           st->current_flags,
 251                                           pg_level[st->level].num);
 252
 253                         pt_dump_seq_putc(st->seq, '\n');
 254                 }
 255
 256                 /*
 257                  * Address indicates we have passed the end of the
 258                  * current section of virtual memory
 259                  */
 260                 note_page_update_state(st, addr, level, val, page_size);
 261         }
 262         st->last_pa = pa;
 263 }
 264
 265 static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
 266 {
 267         pte_t *pte = pte_offset_kernel(pmd, 0);
 268         unsigned long addr;
 269         unsigned int i;
 270
 271         for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
 272                 addr = start + i * PAGE_SIZE;
 273                 note_page(st, addr, 4, pte_val(*pte), PAGE_SIZE);
 274
 275         }
 276 }
 277
 278 static void walk_hugepd(struct pg_state *st, hugepd_t *phpd, unsigned long start,
 279                         int pdshift, int level)
 280 {
 281 #ifdef CONFIG_ARCH_HAS_HUGEPD
 282         unsigned int i;
 283         int shift = hugepd_shift(*phpd);
 284         int ptrs_per_hpd = pdshift - shift > 0 ? 1 << (pdshift - shift) : 1;
 285
 286         if (start & ((1 << shift) - 1))
 287                 return;
 288
 289         for (i = 0; i < ptrs_per_hpd; i++) {
 290                 unsigned long addr = start + (i << shift);
 291                 pte_t *pte = hugepte_offset(*phpd, addr, pdshift);
 292
 293                 note_page(st, addr, level + 1, pte_val(*pte), 1 << shift);
 294         }
 295 #endif
 296 }
 297
 298 static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
 299 {
 300         pmd_t *pmd = pmd_offset(pud, 0);
 301         unsigned long addr;
 302         unsigned int i;
 303
 304         for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
 305                 addr = start + i * PMD_SIZE;
 306                 if (!pmd_none(*pmd) && !pmd_is_leaf(*pmd))
 307                         /* pmd exists */
 308                         walk_pte(st, pmd, addr);
 309                 else
 310                         note_page(st, addr, 3, pmd_val(*pmd), PMD_SIZE);
 311         }
 312 }
 313
 314 static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start)
 315 {
 316         pud_t *pud = pud_offset(p4d, 0);
 317         unsigned long addr;
 318         unsigned int i;
 319
 320         for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
 321                 addr = start + i * PUD_SIZE;
 322                 if (!pud_none(*pud) && !pud_is_leaf(*pud))
 323                         /* pud exists */
 324                         walk_pmd(st, pud, addr);
 325                 else
 326                         note_page(st, addr, 2, pud_val(*pud), PUD_SIZE);
 327         }
 328 }
 329
 330 static void walk_pagetables(struct pg_state *st)
 331 {
 332         unsigned int i;
 333         unsigned long addr = st->start_address & PGDIR_MASK;
 334         pgd_t *pgd = pgd_offset_k(addr);
 335
 336         /*
 337          * Traverse the linux pagetable structure and dump pages that are in
 338          * the hash pagetable.
 339          */
 340         for (i = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
 341                 p4d_t *p4d = p4d_offset(pgd, 0);
 342
 343                 if (p4d_none(*p4d) || p4d_is_leaf(*p4d))
 344                         note_page(st, addr, 1, p4d_val(*p4d), PGDIR_SIZE);
 345                 else if (is_hugepd(__hugepd(p4d_val(*p4d))))
 346                         walk_hugepd(st, (hugepd_t *)p4d, addr, PGDIR_SHIFT, 1);
 347                 else
 348                         /* p4d exists */
 349                         walk_pud(st, p4d, addr);
 350         }
 351 }
 352
 353 static void populate_markers(void)
 354 {
 355         int i = 0;
 356
 357 #ifdef CONFIG_PPC64
 358         address_markers[i++].start_address = PAGE_OFFSET;
 359 #else
 360         address_markers[i++].start_address = TASK_SIZE;
 361 #endif
 362 #ifdef MODULES_VADDR
 363         address_markers[i++].start_address = MODULES_VADDR;
 364         address_markers[i++].start_address = MODULES_END;
 365 #endif
 366         address_markers[i++].start_address = VMALLOC_START;
 367         address_markers[i++].start_address = VMALLOC_END;
 368 #ifdef CONFIG_PPC64
 369         address_markers[i++].start_address = ISA_IO_BASE;
 370         address_markers[i++].start_address = ISA_IO_END;
 371         address_markers[i++].start_address = PHB_IO_BASE;
 372         address_markers[i++].start_address = PHB_IO_END;
 373         address_markers[i++].start_address = IOREMAP_BASE;
 374         address_markers[i++].start_address = IOREMAP_END;
 375         /* What is the ifdef about? */
 376 #ifdef CONFIG_PPC_BOOK3S_64
 377         address_markers[i++].start_address =  H_VMEMMAP_START;
 378 #else
 379         address_markers[i++].start_address =  VMEMMAP_BASE;
 380 #endif
 381 #else /* !CONFIG_PPC64 */
 382         address_markers[i++].start_address = ioremap_bot;
 383         address_markers[i++].start_address = IOREMAP_TOP;
 384 #ifdef CONFIG_HIGHMEM
 385         address_markers[i++].start_address = PKMAP_BASE;
 386         address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
 387 #endif
 388         address_markers[i++].start_address = FIXADDR_START;
 389         address_markers[i++].start_address = FIXADDR_TOP;
 390 #ifdef CONFIG_KASAN
 391         address_markers[i++].start_address = KASAN_SHADOW_START;
 392         address_markers[i++].start_address = KASAN_SHADOW_END;
 393 #endif
 394 #endif /* CONFIG_PPC64 */
 395 }
 396
 397 static int ptdump_show(struct seq_file *m, void *v)
 398 {
 399         struct pg_state st = {
 400                 .seq = m,
 401                 .marker = address_markers,
 402                 .start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
 403         };
 404
 405 #ifdef CONFIG_PPC64
 406         if (!radix_enabled())
 407                 st.start_address = KERN_VIRT_START;
 408 #endif
 409
 410         /* Traverse kernel page tables */
 411         walk_pagetables(&st);
 412         note_page(&st, 0, 0, 0, 0);
 413         return 0;
 414 }
 415
 416
 417 static int ptdump_open(struct inode *inode, struct file *file)
 418 {
 419         return single_open(file, ptdump_show, NULL);
 420 }
 421
 422 static const struct file_operations ptdump_fops = {
 423         .open           = ptdump_open,
 424         .read           = seq_read,
 425         .llseek         = seq_lseek,
 426         .release        = single_release,
 427 };
 428
 429 static void build_pgtable_complete_mask(void)
 430 {
 431         unsigned int i, j;
 432
 433         for (i = 0; i < ARRAY_SIZE(pg_level); i++)
 434                 if (pg_level[i].flag)
 435                         for (j = 0; j < pg_level[i].num; j++)
 436                                 pg_level[i].mask |= pg_level[i].flag[j].mask;
 437 }
 438
 439 #ifdef CONFIG_PPC_DEBUG_WX
 440 void ptdump_check_wx(void)
 441 {
 442         struct pg_state st = {
 443                 .seq = NULL,
 444                 .marker = address_markers,
 445                 .check_wx = true,
 446                 .start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
 447         };
 448
 449 #ifdef CONFIG_PPC64
 450         if (!radix_enabled())
 451                 st.start_address = KERN_VIRT_START;
 452 #endif
 453
 454         walk_pagetables(&st);
 455
 456         if (st.wx_pages)
 457                 pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
 458                         st.wx_pages);
 459         else
 460                 pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 461 }
 462 #endif
 463
 464 static int ptdump_init(void)
 465 {
 466         populate_markers();
 467         build_pgtable_complete_mask();
 468         debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
 469                             &ptdump_fops);
 470         return 0;
 471 }
 472 device_initcall(ptdump_init);